Key Takeaways – Courier | Building a User Notifications strategy at scale (Tommy Dang – Airbnb & Liza Gurtin – Slack):
- Notification Infrastructure is Mission Critical:
- Both Slack and Airbnb built dedicated teams for multi-channel notification infrastructure because notifications are fundamental to product experience and business outcomes (engagement, trust, revenue).
- Scaling notifications requires deep technical investment, as volume and user expectations rise.
- Channel Strategy and Smart Defaults:
- Default channels for Slack: Initially email, then push/in-app once mobile apps are installed. Pushes were suppressed on mobile if the user was active on desktop (attention management).
- Airbnb shifted from a ‘fire on all channels’ approach to a cost and effectiveness-aware cascade (in-app, then push, then SMS/email as needed).
- Notification defaults are absolutely critical, as <5% of users customize settings—most users rely on the experience “out of the box.”
- Managing Signal vs. Noise:
- Slack and Airbnb both built logic and governance to avoid over-notifying users—examples: “silent day” rules (minimum gaps for promo notifications at Airbnb), unique flows for transactional vs. promotional messages, and user-configurable quiet hours (like Do Not Disturb).
- In-context settings (“Would you like to mute notifications on weekends?”) increased user engagement with notification controls.
- Personalization vs. Customization:
- Customization: Users set their own preferences (channels, DND, channel-level settings).
- Personalization: System predicts or adapts notification delivery (Airbnb uses user “fuel points” and ML models; Slack historically focused more on customization due to work context).
- Both approaches have a place; work tools often prioritize giving users direct control, while B2C environments like Airbnb experiment more with automated personalization.
- Tools for Non-Technical Teams:
- Airbnb’s “Omni” and Slack’s “Block Kit” are internal WYSIWYG-style platforms enabling non-engineers (like marketers) to design, target, and send notifications across multiple channels and touchpoints—reducing engineering bottlenecks and accelerating experimentation.
- Team Composition & Ops:
- Small but cross-functional teams, with lots of collaboration between PM, engineering, design, ops, and marketing.
- Notification-related support requests and incidents are high; much of the work is in ensuring clarity, deliverability, and alignment of user expectations.
- Analytics & Deliverability:
- Deliverability (did it reach the user?) and engagement (opens, clicks, reactions) are tracked closely; outages and deliverability drops directly impact business performance.
- Both companies use fallback systems (multiple providers like SendGrid/Sparkpost) to mitigate downtime and optimize deliverability.
- Infrastructure decisions are heavily driven by business needs, volume, and, in Airbnb’s case, legal requirements (regulatory comms).
- Platformization and Governance:
- As notification volume and business complexity grew, both companies invested in governance—manual review, prioritization, and ranking systems (e.g., rank by predicted click-through for simultaneous campaigns).
- Regulatory/mission-critical notifications often have override paths to ensure delivery even if a user has unsubscribed.
These strategies demonstrate how building notification systems at scale is not just a technical challenge but also a product, UX, and organizational one—balancing reach, relevance, business goals, and user trust.
Notifications are the primary way that products communicate with their customers, both in and outside the app, and they’re deeply entangled with how products manage their users’ attention. As the notifications team, that was our charter: to enable Slack users to sort the signal from the noise.
— Liza Gurtin
Once formalized, the team’s charter led them to prioritize where most problems with notifications start: the default state. That is, before any customization, what notifications should Slack send?
Less than 5% of Slack’s users customize their notification settings.
Key Takeaways from “Slack Notification Strategy: Flowchart for Smarter Messaging & Notifications” :
- Notifications are central to Slack’s mission: Slack’s approach centers on managing user attention—too many notifications cause distraction, too few lead to lost engagement.
- Support ticket insights drive design: High volumes of notification-related support tickets pushed Slack to re-evaluate defaults and user control, focusing on meeting actual user expectations.
- Smart defaults build trust: Few users customize notification settings, so Slack prioritizes defaults that balance drawing attention to urgent matters without unnecessary interruptions. For example, desktop notifications are prioritized and mobile push is only sent when the user is inactive.
- User control matters: Slack integrates notification preferences contextually (e.g., prompting users about Do Not Disturb when relevant) to let users fine-tune their experience in meaningful moments.
- Flowchart powers smarter delivery: Slack’s delivery flowchart systematically decides when, where, and how a user should be notified—balancing urgency, relevance, and user availability.
- Design for sustained engagement, not short-term growth: Spammy or excessive notifications may boost quick engagement but ultimately drive user churn and unsubscribes. Slack aims for notifications that deliver long-term value over “growth hacks.”
- Multi-channel best practices: Notify only when needed, let users set preferences, route based on urgency/context, and iterate with clear logic to reduce unsubscribes.
These strategies form a user-first framework for designing multi-channel notification systems that boost long-term engagement.